First of all, very good choice indeed!
You don't need to import anything into Admuncher, it works right out of the box. Jeff maintains that list, so any problems, post here and he will take care of it.
About export, yes you can export your own filter entries (should you have any) to a file. AFAIK you can only use them in another AM installation though; Firefox AdBlock and AM aren't that compatible.

That's not an ad blocker... THIS is an ad blocker.---No bovines were harmed in the making of this program.---My first popup stopper blocked too much.My second popup stopper didn't block enough.Ad Muncher was juuuuust right.

This is being added for v5.x which is under going a complete rewrite to make it more portable and to overcome any short comings in the old filtering engine.

Ad Muncher is very fast though, so adding many entries to your custom list works just as well.

That's not an ad blocker... THIS is an ad blocker.---No bovines were harmed in the making of this program.---My first popup stopper blocked too much.My second popup stopper didn't block enough.Ad Muncher was juuuuust right.